Introduction
I didn’t set out to “become a functional programmer.” I stumbled into Haskell after years of imperative and OOP work, mostly focused on getting features out the door. I knew about lambdas and “map/filter,” but those were just utilities, not a worldview.
My real journey started with the excellent online book Learn You a Haskell for Great Good!. Its playful style made functional programming approachable, and soon I realized Haskell wasn’t just another language—it was a different way to think about programs: where state is explicit, effects are controlled, and types carry meaning.
Why Haskell Was Created
Haskell wasn’t born out of industry needs but out of academic curiosity and a desire for clarity. In the 1980s, researchers had designed many lazy functional languages, but the landscape was fragmented. To unify efforts and create a common foundation, a committee of academics met in 1987 and began the design of what became Haskell, named after the logician Haskell Curry. The goals were ambitious: provide a purely functional language with lazy evaluation, a strong static type system, and mathematical elegance — not for mass adoption at first, but as a laboratory for ideas. Ironically, many of those ideas, from monads to type classes, later inspired mainstream languages like Scala, Rust, and even Java and C#.
Before Haskell: The Default Mindset
My default approach to programming used to be straightforward: keep a mutable model of the world, push data through procedures, and mutate state until it looks right. When bugs appeared, I added guards and logs. If performance dipped, I cached aggressively. It worked—until it didn’t. Debugging felt like chasing shadows in a room full of mirrors.
The Haskell Shock
Haskell flipped the script. The language gently forces you to state what can change, where it can change, and what must remain pure. Instead of sprinkling “fixes” across the code, you model the problem with types and make invalid states unrepresentable. The compiler stops being a nag and becomes a teammate. When it compiles, it often works.
Core Ideas That Rewired My Brain
1) Purity and Immutability
In Haskell, a function’s output depends only on its inputs. No hidden mutations, no global state by surprise. That constraint sounds restrictive at first; in practice, it’s liberating.
2)Variable Destructuring and Recursion
Because Haskell has no traditional for or while loops, recursion is the default way to express repetition. A key enabler of this is pattern matching on function arguments. Instead of writing boilerplate code to check if a list is empty, you destructure it directly in the function definition.
-- Recursively compute the length of a list
length' :: [a] -> Int
length' [] = 0 -- base case: empty list
length' (_:xs) = 1 + length' xs -- recursive case: split head and tail
Here, the list is destructured into its head (_, ignored) and tail (xs). This style makes recursion natural and expressive. You write what a list is in each case, and the compiler enforces that all cases are covered. The same mechanism applies not only to lists but to any algebraic data type you define.
3) Functions as Values
You don’t write loops that mutate counters; you describe transformations on collections. This makes the “what” explicit and hides the “how,” which reads closer to a specification.
4) Partial Function Application
Every Haskell function is curried, meaning you can call it with fewer arguments and get back a new function. This is partial application, and it’s everywhere.
addFive :: Int -> Int
addFive = (+ 5)
-- Now addFive 10 == 15
5) Function Composition
Composition is central in Haskell and expressed by the (.) operator. It connects functions like building blocks.
pipeline :: [Int] -> Int
pipeline = sum . map (*2) . filter (> 10)
By the way, here is a function that in is very definition, makes it a curried function, because tha argument is not define yet in its "body", only in its signature
6) Defining Custom Operators
One of the neat tricks in Haskell is the ability to define your own operators. This lets you write code that reads almost like natural language.
-- Define a new operator for applying a function to a value
(-:) :: a -> (a -> b) -> b
x -: f = f x
-- Example usage:
5 -: (+3) -: (*2) -- evaluates to 16
This style is expressive: you can chain transformations in a way that emphasizes the flow of data rather than nested function calls.
7) Types That Say What You Mean
Haskell’s type system isn’t just about safety—it’s a design language. You model your domain precisely and let the compiler enforce it.
8) Algebraic Data Types and Pattern Matching
With ADTs, you can model alternatives directly. Pattern matching ensures you handle every case.
9) Typeclasses
Instead of OOP inheritance, Haskell uses typeclasses for ad-hoc polymorphism.
10) Laziness
Laziness makes it possible to work with infinite lists and evaluate only what’s needed.
11) IO and Effects
Haskell forces you to separate pure computation from side effects, which makes your code cleaner and more testable.
12) Equational Reasoning
Because of purity, you can replace equals with equals. Refactoring becomes algebra.
Lasting Impact on How I Code (Even Outside Haskell)
- I model first, implement second. I try to make invalid states unrepresentable.
- I isolate effects. Pure core, effectful shell—no matter the language.
- I favor composition, partial application, and custom operators. They reduce boilerplate and clarify intent.
- I trust the typechecker. Even in dynamically typed code, I document data shapes and contracts.
The "Social" Life of Haskell Programmers, chatGPT POV (but still some accurateness inside)
Socially, they live in a state of double marginality: despised by JavaScript developers who find them “too theoretical,” and envied by mathematicians who reproach them for having too much fun with the category of endofunctors. And yet, they persist, convinced that one day the whole world will recognize that the future of computing is written in do notation.
Their humor revolves around puns nobody else understands: “Do you know the joke about the applicative functor?” (awkward silence). They laugh among themselves, then return to writing an experimental compiler that compiles nothing useful but whose syntactic beauty brings a tear to the eye of any code aesthete.
Their lifestyle? Filter coffee, custom mechanical keyboards, and a militant refusal to use an “impure” language at work. That doesn’t stop them from taking a small Python job to pay the rent, which they consider a kind of intellectual prostitution.
In short, Haskell programmers in 2025 resemble digital hermits: misunderstood, eccentric, but convinced they hold in their hands the true definition of elegance.
Conclusion
Discovering the functional paradigm through Haskell changed how I code and how I think. It nudged me from “do this, then that” toward “describe the problem precisely and let the compiler help enforce it.” Even when I’m not writing Haskell, the lessons stick: model with types, separate pure from impure, compose functions, use partial application, and even invent new operators when it improves readability. That shift didn’t just make my programs better—it made programming more enjoyable.